In many surgical procedures involving the cranium, a section of the skull bone (cranium) must be removed to provide access to the brain or other underlying tissue. The section removed may be round, square, or other shape dictated by the nature of the operation, the equipment available, the training of the surgeon, and the like. Following the operation, the bone flap removed must be repositioned and maintained stably for a period of time sufficient to allow the bone to knit together
In the past, two principle methods have been used to secure the bone flap, as illustrated by FIGS. 1a and 1b. In FIG. 1a, a series of holes are drilled adjacent to each other along the mating peripheries of the skull and the bone flap. Wires are inserted through these holes and twisted or tied together to anchor the skull and bone flap in close proximity. The use of such wires causes several problems which are well recognized The protruding wire is apt to cause irritation due to either or both the normal motion of the scalp over the wires, or the palpation of the scalp over the wires Moreover, the protrusion of the wires above the surface of the cranium causes an elevation of the scalp at these positions, which may become more noticeable as scar tissue caused by relative movement of wires and scalp builds over time. This problem is aesthetically displeasing when a portion of the bone flap removed is below the patients hairline, or for balding patients, virtually anywhere. An improvement over the use of wires to maintain a bone flap in position is the use of screw-type devices as illustrated by FIG. 1b. However, these screw-type devices share some of the irritational and in large part, the disfiguring disadvantages of the use of wires.
In U.S. Pat. No. 5,669,912 are disclosed metal pins having two tapering shanks extending from a central protruding collar. One shank is pressed into the bone flap while the other shank is inserted into a hole in the skull positioned to receive the shank. The collar limits the degree of insertion into the bone flap. The device of the '912 patent is illustrated in FIG. 2a, and an application of the device is illustrated in FIG. 2b.
As can be seen in FIG. 2b, the use of the pins of the '912 patent is partially helpful in alleviating irritation and disfigurement by eliminating a number of wires and/or screw-type devices. However, the pins must be positioned parallel to each other and located on the same side of the bone flap, or they will be unable to enter the holes in the skull drilled to receive them. Thus, while one side of the bone flap may be secured with such pins, the remaining sides must be fixed in position with traditional fastening devices such as wires or screw-type fasteners.